An elevator system comprises an elevator cabin and as a rule a compensating weight or counterweight, which can be moved in an elevator shaft or along free-standing guide devices. The elevator cabin and the compensating weight or counterweight can be connected to one another via at least one belt-like carrier means, in order to compensate at least partially for the weight of the elevator cabin. In order to produce the movement, the elevator system has at least one drive with at least in each case one drive wheel which transmits the required drive forces via at least one belt-like drive means to the elevator cabin and optionally to the compensating weight or counterweight.
The carrier means and the drive means can be formed by separate belts, for example in the case of a drum elevator, the carrier means wrapping around pure deflection elements and coupling the elevator cabin and the compensating weight to one another, while the drive means are wound onto the drive wheel. The functions of the carrier means and the drive means are preferably fulfilled by a combined carrier and drive means, which is the case, for example, in what is known as a driving-pulley elevator. Here, at least one belt-like carrier and drive means wraps around at least one drive wheel, the counterweight compensating at least partially for the weight of the elevator cabin and at the same time ensuring the necessary drive capability between the drive wheel and the carrier and drive means.
A belt according to the present invention can be used for each of the above-described functions, that is to say as carrier means, as drive means and also as combined carrier and drive means. It is therefore denoted uniformly in the following text as an elevator belt.
Elevator belts of this type usually comprise a belt body made from an elastomer. In order to transmit the elevator forces, it is known, for example from EP 1 555 234 B1, to embed tensile force carriers in the form of steel and/or plastic ropes in the belt body. In order to increase the contact pressure on the drive wheel and therefore the traction or tractability with the same radial force and therefore the same bearing loading and belt tension, it is known, furthermore, from EP 1 555 234 B1 to configure that contact face of the belt body which interacts with a drive wheel with V-ribs which come into engagement with correspondingly shaped grooves on the running face of the drive wheel. At the same time, the V-ribs ensure the guidance of the elevator belt on the drive wheel.
The use of tensile force carriers in the form of ropes having small diameters makes it possible to use drive wheels having small diameters. The output shaft of the drive can even be configured itself as a drive wheel. Therefore, the following text speaks uniformly of drive wheels, which comprises in equal measure conventional drive pulleys having relatively large diameters but also drive wheels having relatively small diameters and, in particular, also the output shaft of the drive of a elevator system.
Drive and deflection wheels having small diameters have the disadvantage, however, that the tensile force carriers exert a high surface pressure on the belt bodies which surround them in those regions of the elevator belt which in each case rest on a drive or deflection wheel. In particular, if the tensile force carriers also have small diameters, the abovementioned surface pressure can be increased here to such an extent that there is a risk of damaging the belt body. Moreover, in the case of a drive wheel having a low diameter, the traction force is transmitted from the drive wheel via the belt body to the tensile force carriers along a relatively short belt section, which correspondingly has the consequence of high shearing stresses between the belt body and the tensile force carriers.
On account of the above-described effects, damage of the belt body can occur, for example in the form of (micro-) abrasion, shattering of the elastomer which surrounds the tensile force carriers, or tensile force carriers cutting into the elastomer.